sedimentary

Lignite (Brown Coal)

Humic Lignite (Carbonaceous sedimentary rock)

AI-generated identification · may be incorrect

Hardness: 2.5–3.5 on Mohs scale; Color: Dark brown to black; Luster: Dull to earthy; Crystal Structure: Amorphous (non-crystalline); Cleavage: None/Irregular; Specific Gravity: 0.5–1.5 (relatively lightweight)

Hardness: 2
Color: Dark brown to black
Luster: Dull to earthy

Identified March 19, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed from the compression of peat under relatively low heat and pressure. It is considered the lowest rank of coal and represents the transition from peat to bituminous coal. Typically dates from the Tertiary or Cretaceous periods.

Uses & applications

Primarily used as fuel for steam-electric power generation; occasionally used as a source of montan wax or for soil amendments in horticulture due to its organic content.

Geological facts

Lignite is often called 'brown coal' and still contains visible plant structures or 'woody' textures. It has a high moisture content (up to 45%) which makes it less efficient and more polluting to burn than higher-grade coals.

Field identification & locations

Identify by its brownish-black color, relatively light weight, and the presence of visible fossilized organic fibers or wood grain. It is commonly found in large deposits in Germany, North Dakota (USA), Australia, and Russia. Collectors value specimens that clearly show fossilized wood structures.